RESUMO
Amplitude and phase response of ventilation (V<SUB>E</SUB>), carbon dioxide output (VCO<SUB>2</SUB>) and oxygen uptake (VO<SUB>2</SUB>) during sinusoidally varying work load for periods (T) of 1-16 min were studied in six healthy men. The relationships between these parameters and aerobic capacity (VO<SUB>2</SUB>max, ATVO<SUB>2</SUB>) were also examined. The results and conclusions obtained were as follows:<BR>(1) The relationship between the period (T) of exercise and amplitude response of VO<SUB>2</SUB>, VCO<SUB>2</SUB> and V<SUB>E</SUB> was well described by first-order exponential models. However, the relationship between the period of exercise and the phase shift (phase responses of VO<SUB>2</SUB>, VCO<SUB>2</SUB>, and V<SUB>E</SUB>) was better described by complex models comprising a first-order exponential function and a linear equation. This can be explained by Karpman's threshold theory.<BR>(2) High negative correlations were observed between the steady-state amplitude (A) of phase response or the time constants (r) of amplitude response and VO<SUB>2</SUB>max, and ATVO<SUB>2</SUB>. Significantly high negative correlations for all gas exchange parameters may be more rapid in individuals with greater aerobic capacity.<BR>(3) A close relationship between the response of VCO<SUB>2</SUB> and V<SUB>E</SUB> was demonstrated by a higher correlation coefficient than that between VO<SUB>2</SUB> and VCO<SUB>2</SUB> or between VO<SUB>2</SUB> and V<SUB>E</SUB>. This can be partly, but not completely, explained by the cardiodynamic theory.
RESUMO
The purpose of this study was to elucidate the changes in systolic and diastolic time intervals which accrue along with increase of HR during a prolonged exercise.<BR>Fifteen male collegiate distance runners performed bicycle ergometer exercise of 70% maximal oxygen intake for 60 minutes. Electrocardiogram, phonocardiogram, pulse wave using ear densitogram and its derivative were recorded throughout the exercise, and then HR, STI, DT (diastolic time) and QS<SUB>2</SUB>/DT were caluculated from the tracings.<BR>The results obtained are as follows:<BR>1. At the initial phase of the exercise, DT decreased markedly to result in rapid increase of QS<SUB>2</SUB>/DT. When HR was between 130-150 beats/min, however, the rate of decrease of QS<SUB>2</SUB> was greater than that of DT, so QS<SUB>2</SUB>/DT showed a tendency to decrease. When HR was more than 150, QS<SUB>2</SUB> reached a plateau but DT still continued to decrease, and QS<SUB>2</SUB>/DT turned to increase again.<BR>2. LVET decreased slowly throughout the exercise, whereas PEP decreased rapidly within initial two minutes and kept a steady state thereafter. The change in QS<SUB>2</SUB> after two minutes of exercise seemed to depend on LVET.<BR>3. LVETi and QS<SUB>2</SUB>i showed a similar change as that in QS<SUB>2</SUB>/DT but the change in QS<SUB>2</SUB>i was less obvious than that in LVETi.<BR>4. PEN and PEP/LVET decreased rapidly in the initial two minutes, thereafter they continued to increase more slowly with increase of HR until the end of exercise.<BR>Conclusively, HR continued to increase monotonously during prolonged exercise of a constant intensity, while systolic and diastolic time intervals varied the directions and patterns of their changes during the exercise.
RESUMO
The purpose of this study was to investigate the effects of contraction force and the pooled blood volume in the calf on the pumping action of calf muscle contraction. Calf blood volume was controlled by lower body negative pressure (LBNP) and isometric contraction of calf extensor muscle was performed using a handmade dynamometer in recumbent position. The relative volume changes (ΔV/V%) of calf were determined using rubber straingage, when isometric contractions (5, 10, 20, 40 and 60 kg) of the calf muscle were repeated under LBNP of 0, -20, -40, and -60 mmHg.<BR>During resting condition, Δ V/V was increased by 1.04% under -20 mmHg LBNP, 1.88% under -40 mmHg, and 2.54% under -60 mmHg. These increases of ΔV/V were due to the increased blood pooling in the calf. It was shown that the increased blood volume was almost expelled by several bouts of muscle contractions of proper force. The optimum force of contractions for expelling pooled blood was 20 kg under -20mmHg LBNP, and 40 kg under -40 and -60 mmHg LBNP. And it was apparent that the effectiveness of muscle pump was accumulated with repeating contractions, arriving to a plateau after several bouts.<BR>It was shown that the effect of muscle pump in the given contraction force was more effective under the condition with more amount of blood contained in the calf, but the muscle pumping action by light contraction forces couldn't overcome the effect of severe LBNP.
RESUMO
The present investigation was designed to examine the effects of warming-up (W-up) on the blood lactate kinetics during 5 minutes of pedaling exercise. Five healthy male adults were the subjects. The intencity of the criterion task (CT) was about 80% VO<SUB>2</SUB>max, and that of the W-up was a work load corresponding to the anaerobic threshold. Between W-up and CT there were five-minute rest periods on the bicycle ergometer. In order to determine the blood lactate values, blood samples were taken from the antecubital vein at the following times: rest, pre-CT, and 3, 5, 7, and 30-minutes after CT. Expired gas was analysed continuously for the calculation of VO<SUB>2</SUB>, VCO<SUB>2</SUB>, R, VE. The heart rate was recorded every min-ute from ECG.<BR>Blood lactate values increased 3.23±0.91 mmol/<I>l</I> after W-up, a significant increase over the resting values. The peak blood lactate during the W-up experiment (4.62±0.84 mmol/<I>l</I>) was significantly lower than that of the control experiment (6.48±1.69 mmol/<I>l</I>) . Differences in lactate before and after CT (ΔLa) was found to be significantly lower in experiments with W-up (1.39±0.99 mmol/<I>l</I>) as compared with control experiments (5.37±1.62 mmol/<I>l</I>) . In one subject, the blood lactate levels decreased during CT after W-up, while lactate levels increased during CT without W-up. VO<SUB>2</SUB> during CT were very similar in both experiments. These results indicate that this kind of W-up delays the rate of blood lactate accumulation during CT.
RESUMO
The purpose of this study was to investigate the effects of contraction force and the pooled blood volume in the calf on the pumping action of calf muscle contraction. Calf blood volume was controlled by lower body negative pressure (LBNP) and isometric contraction of calf extensor muscle was performed using a handmade dynamometer in recumbent position. The relative volume changes (ΔV/V%) of calf were determined using rubber straingage, when isometric contractions (5, 10, 20, 40 and 60 kg) of the calf muscle were repeated under LBNP of 0, -20, -40, and -60 mmHg.<BR>During resting condition, Δ V/V was increased by 1.04% under -20 mmHg LBNP, 1.88% under -40 mmHg, and 2.54% under -60 mmHg. These increases of ΔV/V were due to the increased blood pooling in the calf. It was shown that the increased blood volume was almost expelled by several bouts of muscle contractions of proper force. The optimum force of contractions for expelling pooled blood was 20 kg under -20mmHg LBNP, and 40 kg under -40 and -60 mmHg LBNP. And it was apparent that the effectiveness of muscle pump was accumulated with repeating contractions, arriving to a plateau after several bouts.<BR>It was shown that the effect of muscle pump in the given contraction force was more effective under the condition with more amount of blood contained in the calf, but the muscle pumping action by light contraction forces couldn't overcome the effect of severe LBNP.